A ureter is one of two ducts which allow the flow of urine from the kidneys to the bladder.

The two ureters run vertically along the spinal column starting from the renal pelvis for 25-30 cm, ending at the bottom of the urinary bladder. They are connected to the posterior wall at the bottom end of the bladder by a valve which prevents the backflow of urine to the kidneys.

The walls of the ureters consist of a mucosal layer in contact with the urine, and a thicker muscular layer which contracts to propel urine towards the bladder.

Some people can have congenital double ureters, which is the presence of two ureters for one kidney. This does not affect the function of the organ.